The invention relates generally to an arrangement for indicating the position of a movable element at a desired location and, more specifically, to an improved electrical arrangement for indicating the desired location.
Such arrangements may be used in particular for indicating a defined position on rotating shafts such as crankshafts, camshafts or similar parts of internal combustion engines.
In the European Pat. No. 0,006,160, the signal generator consists of a support on the stationary casing, which surrounds the moving part, and a dial gauge installed within it with a spring supported contact rod which, on reaching the deepest point in the notch made in the shaft, signals the defined position sought by transmission to the indicator hand of the dial gauge.
Disadvantageous in such an arrangement is the awkward manual determination of the extreme value on the dial gauge which, when mechanically traversing the notch with the contact rod, is only attained at the deepest point in the notch.
Due to the location and installation conditions, the readability of the dial gauge is, on the one hand, often problematical--for example in the case of poor accessibility and lack of light at the reading location--and, on the other hand, the additional space requirement due to the installation height of the dial gauge itself can make its installation difficult or impossible under certain circumstances. It should also be noted that the rotation of the moving part must take place while the dial gauge is being read, in order to find the desired center position and this combination further limits the application or makes it more difficult.
Furthermore, arrangements for the exact setting of the position of two parts relative to one another are mainly used in TDC (top dead center) signal generators as part of diagnosis equipment for motor vehicles. In known arrangements of this type (Siemens-Zeitschrift, Volume 47, 1973, pages 603 to 608), the signal generator (sensor) is installed in the casing, facing a mark on the flywheel of the engine at a defined distance. With every revolution, this mark produces, without contact, a pulse in the signal generator by electro-magnetic means as it passes. These signals can, for example, be evaluated for checking the ignition timing.
Disadvantages of this arrangement are that the signals are from a dynamic measurement, and cannot be produced in the stationary condition, in which an accurate fixing of position should also be possible.
The purpose of the invention is that great accuracy in the desired fixing of the position of previously marked oscillating or rotating machine parts be attainable statically, i.e., in a quasi-rest condition, by means of a device and, on the other hand, that a coincidence indication be also possible remote from the location of the signal generator.
The advantages obtainable using the present invention consist, in particular, in the fact that a device is available at favorable cost with a relatively small outlay. This device permits the determination or fixing of a position with great accuracy on oscillating or rotating machine parts for a wide variety of adjustment procedures. It guarantees a resolution which is unusually high for mechanical devices by the simultaneous point or line contact between two different contact bodies and the object to be inspected. This advantage applies particularly to work on parts of small diameter. A substantial advantage of the invention is, however, also provided by the fact that the signal generator is separately connected as a small component to the machine casing and is only connected by an electrical cable with the otherwise freely movable signalling device with optical and/or acoustic indication. There is therefore no extra space requirement needed for the signalling device and, furthermore, no light is necessary at the indication location. The lighting-up of signal lamps or the sounding of acoustic signals is easier to perceive than a reading from a dial gauge, particularly when it is associated with the simultaneous rotation of the moving part in the area of the position to be found and with poor accessibility to the signal generator.
In the case of reciprocating engines, the arrangement can be advantageously used after the markings have been applied for the static positioning of crankshafts, camshafts, injection pump shafts and distributor shafts.
These and other objects are attained by using a pair of electrically conductive stationary contact regions spaced along the path of a pair of electrically conductive moving contact regions which form a mark at the desired position on the movable element. The stationary contact regions are biased along an axis transverse to the path of and into contact with the moving contact regions. A pair of indicators are connected one to each of the stationary contact regions and to a power source. When the moving contacts are positioned below the stationary contacts at the desired position, both indicators are activated. With the moving contacts electrically connected to the power source, the indicators are electrically in parallel and with the moving contacts electrically isolated from the power source, the indicators are in series. A two-way switch is provided to select the parallel or series connection. The mark may be a recess in or a protuberance on the surface of the movable element. For a recess, the stationary contact regions form a convex shape having a greater angle relative to the transverse axis than the opposed moving contact regions in the recess. For a protuberance, the stationary contact regions form a concave shape having a greater maximum distance of separation than the moving contact regions.
An illustrative example of the invention is shown in the drawing and is described in more detail below.